Apparatus for clamping a workpiece

ABSTRACT

An apparatus wherein a workpiece of indefinite length, e.g., a metal rod, is continuously deformed by a deforming agency to produce a product of indefinite length, e.g., wire. The continuity of the deformation is achieved by intermittently advancing the workpiece into the deforming agency, e.g., a controlled flow of pressurized fluid or a conventional extrusion die, intermittently advancing the deforming agency over the workpiece, and controlling the intermittent advances of the workpiece and the deforming agency to maintain a desired relative velocity between the workpiece and the deforming agency. Also disclosed is a novel workpiece clamping apparatus wherein a segmented cylinder is used as a clamping device for gripping a workpiece.

United States Patent 91 Fuchs Apr. 17, 1973 APPARATUS FOR CLAMPING A 2,732,932 H1956 Strock ..269/34 x WORKPIECE 3,615,154 10/1971 Pryor ..269/34 X [75] inventor: Framiis Joseph Fuchs Princeton Primary ExaminerGranville Y. Custer, Jr.

Junction, NJ. Assistant Examinerl-loward N. Goldberg [731 Assignee: Western Electric Company, lncor- AtwmeyJack Schuman porated, New York, NY. 1

[57] ABSTRACT [22] Filed: May 3, 1971 Appl. No: 139,974

Related US. Application Data Division of Ser. No. 862,673, Oct 1, 1969, Pat. No. 3,696,652.

Field of Search ..269/32-34; 279/2, 4; 72/270 7 References Cited UNITED STATES PATENTS Smith ..269/34 X An apparatus wherein a workpiece of indefinite length, e.g., a metal rod, is continuously deformed by a deforming agency to produce a product of indefinite length, e.g., wire. The continuity of the deformation is achieved by intermittently advancing the workpiece into the deforming agency, e.g., a controlled flow of pressurized fluid or a conventional extrusion die, intermittently advancing the deforming agency over the workpiece, and controlling the intermittent advances of the workpiece and the deforming agency to maintain a desired relative velocity between the workpiece and the deforming agency. Also disclosed is a novel workpiece clamping apparatus wherein a segmented I cylinder is used as a clamping device for gripping a workpiece.

4 Claims, 18 Drawing Figures PATENTEB APR 1 7 I973 SHEET 3 OF 9 PATENTEB APR 1 7 i975 SHEET u [1F 9 PATENTEUAFRIYISB SHEETBUFQ STOP v 45 L36 j STOP PATENTED APR 7 5 SHEET 8 [IF 9 STOPF STOP STOP

STOP

PAIEIIIED I7 75 SHEET 9 [1F 9 FLUID T CONTROL ELEMENT L T DOWNSTREAM CLAMP RADIAL SUPPORT FLUID PRESSURE AND UPSTREAM CLAMP POSITION EXTRUSION FLUID PRESSURE ENGAGED DISENGAGED FILLING FIRST CHAMBER DISENGAGED ENGAGED PUMPING o Em a o Em wmDmmmma wmDmmmmm APPARATUS FOR CLANIPING A WORKPIECE CROSS REFERENCE TO RELATED APPLICATION This application is a division of application Ser. No. 862,673 filed Oct. 1, 1969, now U.S. Pat. 3,696,642, issued Oct. 10, 1972.

BACKGROUND OF THE INVENTION 1 Field of the Invention I This invention relates to the deformation of material 0 to form a product, and in particular, to a method and apparatus which is useful for continuously deforming 'a workpiece, e.g., rod, to form a product, e.g., wire. This invention is particularly useful in passing an indefinite length of rod against a deforming agency to deform the rod, thereby continuously extruding the rod to form wire.

2. Description of Prior Art There have been many approaches to deforming 2O material to form a product, and in particular, to extruding material to form an extrusion product. One of the earliest methods of extrusion involves positioning a billet within a billet container having one end thereof closed by an extrusion die, and exerting a force on the billet, e.g., by an advancing ram, so as to force the billet through the extrusion die. The dimensions of the inner surface of the billet container and the outer surface of the billet are substantially identical so that during extrusion, deformation of the billet material, other than through the extrusion die, is precluded.

An improvement in extrusion processes was the development of hydrostatic extrusion. This type of extrusion involves positioning a billet within a billet container having an extrusion die positioned in one end, and surrounding all but the die-adjacent surface of the billet with a pressure transmitting fluid so as to exert a high pressure thereon and extrude the billet material through the die. This process reduces the amount of work necessary to accomplish extrusion in that the friction between the surface of the billet material and the surface of the billet container is eliminated by the presence of the pressurizing fluid therebetween. Extrusion such as this is shown in greater detail in Canadian Pat. No. 476,793 to P. W.

Bridgman which issued on Sept. 1 l, 1951.

Notwithstanding the reduction of the work necessary to accomplish extrusion afforded by the hydrostatic extrusion method of Bridgman, the amount of work required for extrusion continued to be undesirably high.

A recent development in processes for extruding materials includes the concept of eliminating billet die interface friction by passing the material through a controlled flow of pressurized fluid, which fluid deforms the material in the manner desired. This method is discussed in detail in my copending application Ser. No. 862,677, filed on Oct. 1, 1969, now U.S. Pat. No. 3,677,048, issued July I8, 1972 for METHOD OF POSITIVE FLUID FLOW EXTRUSION, and assigned to the same assignee as the present application.

I-Ieretofore, processes for extruding materials have dealt primarily with the extrusion of discrete billets,

crete billets. For example, it has been suggested that a high-pressure fluid container for containing a billet and having a die at one end be adapted to receive intermittent chargings of coiled billet material into the container. Thereafter, the billet material is extruded through the die until the charge of material within the container is uncoiled. An extrusion process of this typeis shown in the patent to Alexander et al. U.S. Pat. No. 3,415,088 which issued on Dec. 10, 1968. In such processes, however, extrusion is an intermittent, i.e., discharge of extrusion product is not accomplished at a constant rate but rather is interrupted each time the billet container must be recharged with billet material.

A primary obstacle in the development of a continuous, noninterrupted extrusion process has been the trend in extrusion processes to accomplish deformation in a generally high pressure environment. Specifically, the available methods of feeding billet material into such a high pressure environment have not been satisfactory. In order to continuously advance an indefinite length of rod into a high pressure environment, it is necessary that an axial stress be built up in the rod as it is passed from an ambient environment, e.g., substantially zero or room pressure, into the high pressure environment, e.g., pressure in an amount at least equal to that pressure necessary to accomplish deformation of the material. Further, once the material has entered the high pressure environment, care must be taken to avoid deformation, e.g., by sinking or bulging, except as desired.

Since the material to be extruded is subjected to both radial and axial stresses when entering and when in the high pressure environment, it can be recognized that if the net stress built up in the material is in excess of the rod yield strength at any point, ruinous deformation such as rod sinking or pinch-off, i.e., deformation in an axial direction, or rod bulging, i.e., deformation in a radial direction, may occur. In order to prevent rod bulging, radial support pressure must be applied to the rod, commencing at the entry to the high pressure environment, which support pressure must be of sufficient magnitude to counteract the axial stress in such a manner as to insure that the axial stress in the rod does not exceed the radial stress generated by the support pressure by an amount greater than the yield strength of the rod material. However, the radial support pressure must be controlled so as to not generate a radial stress which exceeds the axial stress by an amount greater than the rod yield strength, otherwise, sinking or pinch-off will occur. Thus, in order to satisfactorily i.e., billets of definite length, which length is determina- 6 ble and limited by the size of the extrusion apparatus. Recent developments in the extrusion arts, however, have been directed toward the extrusion of non-discontinuously deform an indefinite length of rod which is introduced from a low pressure environment, e.g., an atmospheric environment, to a high pressure environment, e.g., a high pressure fluid chamber, the axial stress and the radial stress in the rod being fed must be controlled in such a manner as to preclude either of the stresses exceeding the other by an amount in excess of the yield stress of the rod material, except in a zone of deformation wherein deformation of the rod is accomplished as desired to form a product of indefinite length.

One approach to feeding a rod into a high pressure environment for purposes of continuous hydrostatic extrusion through a die is disclosed in copending application Ser. No. 794,488, filed Jan. 28, 1969, now aban-' doned in favor of Continuation-in-Part application Ser. No. 876,940 filed Nov. 14, 1969, now US. Pat. No. 3,677,267, issued June 6, 1972 for VISCOUS DRAG FEEDING METHODS.

SUMMARY OF THE INVENTION The present invention relates to a method for deforming a workpiece of indefinite length to form a product of indefinite length.

In this regard, a method according to the invention may include the steps of intermittently advancing a workpiece into a deforming agency, intermittently advancing the deforming agency onto the workpiece, controlling the intermittent advances of the workpiece and the deforming agency to maintain a desired relative velocity between the workpiece and the deforming agency, and continuously deforming the workpiece by the deforming agency to produce the product.

In addition to the above-summarized deformation process, the present invention also contemplates a novel workpiece clamping device. Such a workpiece clamping device may include a plurality of longitudinally extending cylinder segments, means for displacing the segments into workpiece engaging position and means for displacing the segments into workpiece disengaging position.

BRIEF DESCRIPTION OF THE DRAWING A' more complete understanding of the present invention may be had from a consideration of the following detailed description particularly when considered in the light of the accompanying drawings wherein:

FIG. 1 is a partial perspective view of an apparatus for deforming according to the method of the inventron;

FIGS. 2a, b and c are cross-sectional elevational views through theplane 2-2 of FIG. 1i

FIG. 3 is a key plan showing the figure relationship for considering FIGS. 2a, b and c,

FIG. 4a is a partial elevational, cross-sectional view of the upstream rod clampingdevice utilized in the apparatus of FIG'. 1;

FIG. 4b is a partial elevational, cross-sectional view of the downstream rod clamping device utilized in the apparatus of FIG. 1;

FIG. 5a is a partial cross-sectional view through the plane 5a--5a of FIG. 4a;

FIG. 5b is a partial cross-sectional view through the plane Sb-Sb of FIG. 4b;

FIG. 6a through h are schematic views of the apparatus of FIG. 1 showing various relative motions and apparatus positions during the operation of the apparatus of FIG. I; and

FIG. 7 is a timing chart showing the position, velocity and pressure condition of various elements and systems of the apparatus of FIG. 1 during operation.

DETAILED DESCRIPTION 7 operation of apparatus 10, a rod 12 of indefinite length continually passes into the upstream" end of apparatus 10 wherein it is continuously extruded by a deforming agency and discharged as an extrusion product, e.g., wire 14, at the downstream end of the apparatus.

The rod 12 passing into apparatus 10 passes initially through an aperture 15 (FIG. 2a), having a sizing die surface 16, in a rigidly mounted base 17. Sizing die surface 16 provides ameans for correcting any oversize faults in rod 12 as it passes into apparatus 10. Base 17 defines a rigid mounting means for a stationary clamp support pedestal 19 and a pair of fluid motors 20, 21 which cooperate to provide reciprocating motion to the upstream portion 22 of a reciprocating clamp cylinder, designated generally by the reference numeral 23, through rods 24 and 25 respectively.

As is discussed in detail below,.reciprocating clamp cylinder 23 comprises an upstream portion 22 and a downstream portion 28 which extend slidably through a pressure vessel designated generally by the reference numeral 30. Pressure vessel 30 comprises an upstream block 32, an intermediate block 33, and a downstream block 34. Upstream block 32 and intermediate block 33 are disposed coaxially and joined by a securing ring 29. Similarly, intermediate block 33 and downstream block 34 are disposed coaxially and joined by a securing ring 36. Extending through securing rings 29 and 36 are a plurality of support fluid supply lines 31 and extrusion supply lines 37, respectively.

Formed on the upstream end of the upstream portion 22 of cylinder 23 is an enlarged connector head 38 to which rods 24 and 25 are secured. Similarly, formed on the downstream end of the downstream portion 28 of reciprocating clamp cylinder 23 is an enlarged connector head 39 to which are secured a pair of rods 40 and 41. Rods 40 and 41 connect the downstream-portion 28 of reciprocating clamp cylinder 23 to a pair of fluid motors 42, 43 which cooperate with fluid motors 20 and 21 to provide reciprocating motion to the downstream portion 28 of reciprocating clamp cylinder 23. Fluid motors are provided at each end of clamp cylinder 23 so that the reciprocating of the clamp may be accomplished while maintaining the cylinder in a state of compression. Specifically, the axial stresses generated in cylinder 23 during the operation of apparatus '10 may become of sufficient magnitude to exceed the tensile yield strength of the cylinder material. In order to avoid this problem, which if uncompensated would result in the deformation of cylinder 23 and the failure of apparatus 10, opposed fluid motors 20, 21 and 42, 43 generate a compressive prestress in cylinder 23, which pre-stress enables cylinder 23 to be stressed in tension during the operation of the apparatus 10 without a resultant failure in the cylinder.

Extending slidably through an opening 44 in connector head 39 is a ram 45 which is secured to a piston rod 47 by a coupling 48 having an aperture 50 therein for allowing the discharge of wire 14. Piston rod 47 is connected to a fluid motor (not shown) for imparting reciprocating movement to ram 45 within the downstream portion 28 of cylinder 23.

Referring to FIGS. 2a, b and c collectively in the relationship shown in FIG. 3, pressure vessel 30 can be seen to comprise upstream block 32, intermediate block 33 and downstream block 34 which are secured in spaced coaxial relationship by threaded securing rings 29 and 36. Intermediate block 33 and downstream block 34 are provided with coaxial, longitudinally axially extending throughbores 55 and 56, respectively, which cooperate with an aperture 57 in upstream block 32 to define a bore extending through pressure vessel for slidably accommodating reciprocating clamp cylinder 23 therein. As noted above, clamp cylinder 23 comprises an upstream portion 22 and a downstream portion 28. The two portions are joined at a threaded mating joint 52. The diameter of aperture 57 in upstream block 32 is substantially equal to the outside diameter of the upstream portion 22 of clamp cylinder 23. Further, the downstream surface of aperture 57 is tapered to define an annular recess to accommodate the mounting therein of a high pressure seal structure 59. Seal structure 59 is shown to comprise an O-ring soft seal and an anti-extrusion ring. It should be recognized, however, that any high pressure seal structure which is suited for use in sealing the space between relatively movable surfaces may be used.

The downstream portion 28 of clamp cylinder 23 is provided with a stepped outer surface having a downstream portion 61, the diameter of which is substantially equal to the diameter of throughbore 56, and an upstream portion 63, the diameter of which is substantially equal to the diameter of throughbore 55. Downstream surface portion 61 and upstream surface portion 63 are longitudinally separated by a relieved portion 65, the diameter of which is discussed below in detail. The shoulders defined by the junctures of relieved portion 65 with downstream surface portion 61 and upstream surface portion 63 are shaped to accommodate the mounting of high pressure seals 67 and 68, respectively.

Mounted coaxially with and between intermediate block 33 and downstream block 34 is an annular extrusion fluid distribution ring 70. Both the upstream and downstream radial surfaces 72, 73 of ring 70 are provided with first relieved portions 75, 76 which cooperate with annular shoulders formed on the corners of blocks 33 and 34 to define annular spaces for receiving high pressure seals 78 and 79 respectively. Spaced radially inwardly of first relieved portions 75, 76 are second relieved portions 81, 82 which define annular spaces into which extrusion fluid may be discharged as is discussed below. The inner circumferential surface of extrusion fluid distribution ring 70 is provided with an annular channel for mounting an 0- ring seal 84, which seal precludes the passage of fluid between the inner surface of ring 70 and the surface of relieved portion 65 of the downstream portion 28 of clamp cylinder 23.

The upstream surface 63 of the downstream portion of clamp cylinder 23 is relieved at its upstream end and cooperates with the upstream portion 22 of cylinder 23 to define an annular space for receiving a high pressure seal 85.

The outer circumferential surface of upstream portion 22 cooperates with the surface of throughbore 55, seal 59 and seal 86 to define an annularouter chamber 90 for containing support fluid. Similarly, the surface of relieved portion 65 cooperates downstream of ring 70 with throughbore 56, seal 67 and second relieved portion 82 to define an outer annular extrusion fluid chamber 92. Upstream of ring 70, relieved surface 65 cooperates with second relieved portion 81, throughbore 55 and seal 68 to define an annular clamp actuating fluid chamber 94. Annular outer extrusion fluid chamber 92 and clamp actuating fluid chamber94 vary in volume during operation of apparatus 10 in that the longitudinal displacement of reciprocating clamp cylinder 23 causes relieved portion 65 to slide longitudinally back and forth within stationary ring 70.

Extrusion fluid is provided to fluid chambers 92 and 94 through passages formed in extrusion fluid distribution ring 70. Specifically, as noted above, extrusion fluid source lines 37 pass radially inwardly throughsecuring ring 36 at four positions around vessel 30. The positioning and number of source lines 37 are arbitrary, however, in the apparatus 10, four lines are shown spaced at 90 intervals around ring 36. The inner ends of lines 37 are each tapered conically and received in complementarily tapered orifices 96 formed at 90 intervals in the outer circumferential surface of ring 70. Each orifice 96 communicates with an extrusion fluid branch passage 98 and a clamping fluid branch passage 99 through a radially directed fluid passage 101.

Extrusion fluid branch passage 98 extends from passage 101 to the second relieved portion 82 of the downstream radial surface of ring so as to communicate outer extrusion fluid chamber 92 with a source of extrusion fluid (not shown) through passage 99 and fluid line 37. Flow of fluid through branch passage 98 is limited by a spring ring check valve 103 which covers the opening of passage 98 into second relieved portion 82 in such a manner as to preclude flow of fluid out of chamber '92, and to limit the flow of fluid into chamber 92 to situations wherein the pressure of the fluid in passage 98 is sufficient to overcome the spring load of ring check valve 103.

Clamping fluid branch passage 99 extends from passage 101 to the second relieved portion 81 of the upstream radial surface of ring 70 and provides for the unobstructed communication of clamp actuating fluid chamber 94 with a source of extrusion fluid (not shown) through passage 101 and fluid line 37. Extrusion fluid distribution ring 70 is maintained in position and supported radially by a segmented cylinder 104, which is in surface-to-surface engagement with the outer peripheral surface of ring 70. Cylinder 104 is supported radially by hearing against the inner peripheral surface of securing ring 36. The inner tapered end of fluid line 37 is maintained in surface-to-surface engagement with the tapered surface 96 of ring 70 by the cooperation of a bored plug 105 bearing against the surface of a collar 106 which is threaded on fluid line 37. Thus, by tightening bored plug 105 within the threaded aperture in securing ring 36, the lower surface of the plug bears against the upper surface of collar 106 thereby forcing line 37 to which collar 106 is secured, rigidly against tapered surface 96. It should be noted that the threads on plug 105 and on collar 106 should be opposite-hand so that rotation of plug 105 during tightening will not be accompanied by a corresponding rotation of collar 106 as a result of the frictional engagement therebetween.

Fluid is introduced to outer support fluid chamber from support fluid supply line 31 through a support fluid distribution ring 107. Ring 107 is similar to extrusion fluid distribution ring 70 in that it is provided with relieved portions on its upstream and downstream radially extending surfaces to cooperate with annular shoulders on upstream and intermediate blocks 32, 33 to define annular channels for mounting high pressure seals 108 and 109 respectively. Further, ring 107 is provided with a plurality of radially extending passages 110 having conically relieved outer portions for receiving the tapered ends of supply lines 31. Ring 107 is maintained and supported radially by a segmented cylinder 111, bored plug 112 and a collar in the same manner discussed above with respect to ring 70.

Formed through the major portion of the upstream portion 22 of clamp cylinder 23 is a longitudinally axially extending bore 113. Bore 113 communicates with the downstream end of portion 22 through a coaxial, longitudinally extending counterbore 114. Slidably received within bore 113 is generally cylindrical stationary clamp support pedestal 19. Support pedestal 19 is provided with a first bore 115 adjacent its downstream end for accommodating the mounting of a stationary rod clamping device, designated generally by the reference numeral 116, as is discussed in detail below, a second bore 118 of a diameter slightly larger than the diameter of rod 12 so as to provide for the free passage of fluid in an annular space 119 defined therebetween, and a third bore 120 the diameter of which is substantially equal to the diameter of rod 12. Annularspace 119 provides for the introduction of clamp opening fluid to stationary rod clamp 116 from a fluid source (not shown) through a fluid supply line 122 and access passage 124.

The space bounded by the downstream end of stationary rod clamp 116, rod 12, bore 113, the upstream end of a reciprocable rod clamp designated generally by the reference'numeral 130, and counterbore 114 defines an inner support fluid chamber 126 which is in communication withouter support fluid chamber 90 through .a plurality of radially extending passages 127. As is discussed below in detail, the.diameter of counterbore.l12 is somewhat larger than the diameter of rod 12 so as to allow the passage of support fluid through the annular space defined thereby, which fluid acts as a clamp opening fluid for reciprocable rod clamp 130.

The downstream portion 28 of reciprocating clamp cylinder 23 is provided with a first bore 132 which extends longitudinally axially from the upstream end thereof to a second longitudinally axial bore 133 which is smaller in diameter than first bore 132. Bore 133, in turn, extends from first bore 132 to a third bore 134 which comprises a continuation of opening 44 in enlarged head 39 (FIG. 1) and which extends throughout the major length of portion 28. First bore 132 is provided with a first threaded surface for cooperating with upstream portion 22 to define threaded mating joint 52. A second threaded surface is provided in first bore 132 to accommodate the mounting of reciprocable rod clamp 130 therein.

Slidably received in second bore 134 is a fluid control element 136 which is mounted on the upstream end of ram 45 for reciprocating movement therewith. Fluid control element 136 is mounted on the end of ram 45 by a threaded mating connection 138. Similarly, for ease of assembly, downstream portion 28 of reciprocating clamp cylinder 23 is made in sections and joined by a threaded mating joint 139. A portion of the inner surface of downstream portion 28 is relieved adjacent mating joint 139 so as to accommodate the mounting of a high pressure seal 140 which is secured in position by a threaded retaining cylinder 141. Sea] 140 precludes the flow of fluid out of an inner extrusion fluid chamber 142 past fluid control element 136 through third bore 134.

Formed in the upstream end of fluid control element 136 is an axially extending convergent opening defined by a tapered conical flow control surface 137. The opening defined by flow control surface 137 communicates at its downstream end with an axially extending passage 143 formed in fluid control element 136 and ram 45 to accommodate the discharge of extrusion product from the fluid control element, through ram 45 and out aperture 50 in coupling 48. As is discussed below, the deformation of rod 12 occurs as a result of pressures applied thereto by fluid flowing between the surface of the rod and flow control surface 137. Thus, the axial length of flow control surface 137 defines a zone of deformation wherein occurs the deformation of rod 12 in producing wire 14.

Mounted in second bore 133 of the downstream-portion 28 of reciprocating clamp cylinder 23 is a thinwalled cylinder 144, the inner diameter of which is the same as the diameter of third bore 134. Thin-walled cylinder 144 is provided with a plurality of apertures which are positioned to be misaligned with a plurality of longitudinally and radially spaced ports 145 formed in downstream portion 28. Ports 145 provide for the communication of outer extrusion fluid chamber 92 with inner extrusion fluid chamber 142 through the apertures in thin-walled cylinder 144. In this regard, thin-walled cylinder is manufactured from a relatively flexible material such as berylium copper so as to act as a check valve. More specifically, when the pressure in outer extrusion fluid chamber 92 is sufficiently in excess of the pressure in inner extrusion fluid chamber 142 to cause radially inward deflection of cylinder 144, ports 145 are uncovered and fluid flows from outer chamber 92, through ports 145 and the aperturesin cylinder 144 to inner extrusion fluid chamber 142. However, when the pressure in inner extrusion fluid chamber 142 is in excess of the pressure in outer extrusion fluid chamber 92, cylinder 144 is displaced radially outwardly so as to cover ports 145 thereby precluding fluid flow from inner chamber 142 to outer chamber 92.

Considering now stationary and reciprocable rod clamps 116 and 130 respectively, the structure of each of these clamps is identical except for the manner in which clamp engaging fluid is provided to the outer surface of the clamp. Accordingly, the structure and operation of the clamps will be considered concurrently, and where appropriate, like reference numerals will be used to indicate like structure. In this regard, with reference to FIGS. 4a, b and FIGS. 5a and b, FIG. 4a shows stationary rod clamp 116 in rod engaging position, FIG. 4b shows reciprocable rod clamp 130 in rod releasing position, FIG. 5a is a cross-sectional view through the plane 5a5a of FIG. 4a, and FIG. 5b is a cross-sectional view through the plane 5b-5b of FIG. 4b.

Referring to FIG. 4a, therefore, stationary rod clamp 116 is shown positioned concentrically between the I downstream portion 22 of reciprocating clamp cylinders 23 and rod 12. The overall clamp structure includes an upstream sealing block 146 and a downstream sealing block 148 between which is positioned a rod clamping cylinder 150.

Referring particularly to FIGS. 4a and 5, rod clamping cylinder 150 can be seen to be a segmented cylinder defined by a plurality of tapered segments 152. Each segment 152 has an outer circumferential surface 154, an inner circumferential surface 155, and radially extending longitudinal surfaces 156 and 157 (FIG. The outer edges of surfaces 156 and 157 are tapered to define passages 158 for accommodating the free flow of clamp closing fluid as is discussed in detail below. Additionally, each of radial surfaces 156 and 157 are provided with complementary, trapezoidally shaped channels 159, 160 which cooperate to define a seal receiving channel 161. Each of channels 161 contains a pair of cross-sectionally triangular anti-extrusion strips 163, 164 which are separated by a strip 165 of circular cross-sectional sealing material.

Each radial surface 157 is also provided with a longitudinally extending channel which cooperates with the radial surface 156 of a next-adjacent segment 152 to define a clamp opening fluid passage 168 as is discussed in detail below.

Considering the outer circumferential surfaces 154 of segments 152 collectively, i.e., as the outer circumferential surface 170 (FIGS. 40 and b) of rod clamping cylinder 150, surface 170 is threaded so as to cooperate with complementary threads on the inner surface of first bore 115 of pedestal l9 (clamp 116, FIG. 4a), and with complementary threads on the inner surface of reciprocating clamp cylinder 23 (clamp 130, FIG. 4b). The threaded engagement between surfaces 170, cylinders 22 and the bore 115 of pedestal 19 is such as to allow radial movement of segments 152 into and out of engagement with rod 12 during the operation of the apparatus. Further, inward displacement of segments 152 provides spaces between threaded surfaces 170 and the cooperating communication of fluid between passages 158 around the surface of cylinder 150.

The inner circumferential surfaces 155 of segments 152 when considered collectively, i.e., as the inner circumferential surface 172 (FIGS. 4a and b) of rod clamping cylinder 150, define a surface for positively engaging and gripping rod 12. Specifically, surface 172 is provided with shallow teeth 173 which, when the clamp segments 152 are in rod engaging position (FIG. 4a) bite into the surface of the rod and positively grip the rod such as to preclude slippage between the rod and the clamp.

An additional function of'shallow teeth 173 is to provide an axial stress gradient in the material of rod 12 when either of clamps 116 or 130 is engaged. As is discussed below, the operation of apparatus generates axial stress in rod 12 between the zone of deformation in fluid control element 136 and whichever of clamps 116 or 130 is supporting rod 12 at that timev The teeth 173 of clamps 116, 130, when engaged with rod 12, each carry an incremental amount of the axial force on rod 12 generated by the deforma tion thereof through fluid control element 136, thereby reducing the axial stress in the rod. Thus, the axial stress in rod 12 is gradually reduced, i.e., an axial stress gradient is established, along the length of rod 12 which is engaged by teeth 173. It should be recognized that the same effect can be accomplished without teeth 173 by merely relying on a surface-to-surface frictional engagement between rod 12 and clamps 116 and 130. Such an arrangement, however, would substantially increase the length of the clamps, i.e., by an amount sufficient to duplicate the axial load carrying capacity of the toothed surface, which increased length would merely add to the required overall length of the apparatus.

Each upstream sealing block 146 comprises an annular ring having a generally rectangular cross-sectional configuration. Each ring is provided with a downstream surface 175, an upstream surface 176, an outer circumferential surface 177 and an inner circumferential surface 178. Downstream surface is in surface-to-surface engagement with the upstream end of clamping cylinder 150 and is provided with a trapezoidally shaped annular channel for receiving a high pressure seal 180. Seal 180 is positioned adjacent seal receiving channel 161 and precludes the radial passage of fluid either radially inwardly or outwardly around the upstream ends of strips 163, 164 and 165.

Outer circumferential surface 177 is provided with a trapezoidally shaped annular channel for receiving a high pressure seal 182 which prevents the passage of fluid between the outer surface of sealing block 146 and the inner surface of first bore 115 (FIG. 4a) or first bore 132 (FIG. 4b). The inner surface 178 of block 146 is of a diameter substantially equal to the diameter of rod 12 to minimize the passage of fluid therebetween while allowing rod 12 to slide freely therethrough.

Formed in block 146 are a plurality of generally longitudinally extending passages 183 which provide for the communication of fluid from annular space 119 (FIG. 4a) and counterbore 112 (FIG. 4b) to fluid passages 168 in clamps 116 and 130 respectively. Passages 183, at their downstream end, communicate with an annular channel 185 formed in the downstream surface of block 146. Provision of channel 185 obviates the necessity to align passages 183 in block 146 with passages 168 in cylinder 150, and insures that fluid communication between passages 183 and 168 is maintained.

The downstream sealing block 148 (FIG. 4a) associated with stationary sealing clamp 116 comprises an annular ring having upstream and downstream radial surfaces 187, 188, an outer circumferential surface 189 and an inner circumferential surface 190. Outer surface 189 is provided with threads 192 on a portion of its length, which threads cooperate with threads on the inner surface of first bore 115 to secure block 148 in position against rod clamping cylinder 150.

The upstream surface of 187 of block 148 is provided with an annular trapezoidal channel for receiving a high pressure seal 194 which, in the same manner as seals 180 in blocks 146, prevents leakage of fluid around the ends of strips 163, 164, 165 in seal receiving channel 161.

Inner circumferential surface of block 148 is relieved to define an annular channel 196 in which an annular sealing ring 197 is positioned. The unrelieved portion of surface 190 is of a diameter slightly smaller than rod 12 to provide surface-to-surface contact seal between block 148 and rod 12 the purpose of which-is discussed in detail below. Formed in the surface of annular channel 196 is a smaller annular channel 199 to which there extends, from downstream surface 188, a plurality of fluid passages 201. Similarly, channel 199 is in communication with an annular channel 202 formed in first bore 115 through a plurality of passages 204.

Free communication between channels 196 and 199 is prevented by a spring ring check valve 206 which permits fluid to pass from channel 199 to channel 196, but only when the pressure of fluid in channel 199 is sufficient to deflect spring ring 206.

Referring to FIG. 4b, reciprocable rod clamp 130 can be seen to comprise a rod clamping cylinder 150 positioned between an upstream sealing block 146 and a downstream sealing block 208. Downstream sealing block 208 is of the same general configuration as downstream sealing block 148 discussed above with the exception that block 208 is secured against a shoulder 210 defined at the intersection of first bore 132 with second bore 133, both in the downstream section 28 of clamp cylinder 23, and thus the outer surface of block 208 is not threaded.

Block 208 is provided with upstream and downstream surfaces 212, 213, an outer circumferential surface 214 and an inner circumferential surface 215. Upstream surface 212 of block 208 is in surface-to-surface engagement with the downstream end of clamping cylinder 150 and is provided with a trapezoidally shaped annular channel for receiving'a high pressure seal 217. Sea] 217 is positioned adjacent seal receiving channel l6l and precludes the radial passage of fluid, either radially inwardly or outwardly around the downstream ends of strips 163, 164 and 165. In a similar manner, outer circumferential surface 214 is provided with a trapezoidally shaped annular channel for receiving a high pressure 'seal 218 which prevents the passage of fluid between the outer surface 214 of sealing block 208 and the inner surface of first bore 132 (FIG. 4b).

Inner circumferential surface 215 of block 208 is relieved to define an annular channel 220 in which is positioned an annular sealing ring 197 which is the same 'as ring 197 discussed above with respect to FIG. 4a. The unrelieved portion of surface 215 is ofa diameter slightly smaller than rod 12 to provide a surfacetosurface contact seal between block 208 and rod 12. Formed in the peripheral surface of annular channel 220 is an annular channel 222 which is in connection with an annular channel 224 formed in the surface of first bore 132 through a plurality of fluid passages 225.

Free communication between channels 220 and 222 is prevented by a spring ring check valve 227 which permits fluid to pass only from channel 222 to channel 220, and then only when the pressure of fluid in channel 222 is sufficient to deflect spring ring 227.

Annular sealing rings 197 may be formed of resilient material such as rubber and are provided with a tapered surface on their upstream ends which complements and is engageable with a tapered surface in annular channel 220. The outer circumferential surface and downstream surface of annular sealing ring 197 are provided with relieved portions which define passages 229 for the accommodation of fluid therethrough. The inner diameter of annular sealing ring 197 is substantially equal to the diameter of rod 12 so as to allow the sliding passage of rod 12 therethrough when seal 197 is not under load so as to be in sealing engagement with rod 12 as is discussed in detail below.

The operation of clamps 116 and is best considered with reference to FIGS. 2a, 2b, 4a, 4b, 5a and 5b. More specifically, each of clamping cylinders are subjectable to two distinct bodies of fluid, viz. a body of clamp closing fluid which bears against the outer surface of rod clamping cylinder 150 which tends to displace segments 152 radially inwardly, and a clamp opening fluid which is circulated within cylinder 150 through passages 168 and which tends to displace segments 152 radially outwardly. Thus, considering ini tially FIG. 5a which shows clamping cylinder 150 in rod engaging position, clamp opening fluid is present in passages 168 and tends to displace segments 152 radially outwardly. Clamp closing fluid is provided within passages 1'58 and circulating around the threaded outer surface 170 so as to bear against the outer surface 170 of clamping cylinder 150, thereby tending to displace segment 152 radially inwardly. The clamp closing fluid, however, is at a pressure sufficiently greater than the clamp opening fluid to overcome the effect of the clamp opening fluid thereby causing segments 152 to be displaced radially inwardly so as to cause the engagement of shallow teeth 173 with the surface of rod 12. In order to open clamping cylinder 150, the pressure of the fluid in channels 168is made to be such,

either by increasing the clamp opening fluid pressure or decreasing the clamp closing fluid pressure, that the force generated thereby is in excess of the force generated by the effect of clamp closing fluid against outer surface 170. Thus, because of the force disparity,

segments 152 are displaced radially outwardly away.

from rod 12 from the position shown in FIGS. 4a and 5a to the position shown in FIGS. 4b and 5b, and rod release o'ccurs.

- As rod release occurs, fluid flows downstream along the surface of rod 12 within shallow teeth 173 to bear against the upstream surface of seal 197. The pressure of this fluid causes a downstream displacement of seal 197 away from clamping cylinder 150 thereby allowing the free circulation of fluid within annular channel 196 (220 in FIG. 4b). Passage of fluid out of annular channel 196 (220) is precluded by the sealing effect of surfaces (FIG. 4a) and 215 (FIG. 4b), and spring check valves 206 (FIG. 4a) and 227 (FIG. 4b). Thus, when clamps 116 and 130 are in their open position, seals 197 are displaced downstream within channels 196 and 220 respectively. In this regard, the amount of downstream displacement ofv seals 197 is relatively small so as to maintain a high resistance flow path along the tapered surface of seals 197 for reasons discussed below.

When the pressure of clamp closing fluid bearing against surface 170 is increased so as to close clamps 116 and 130, it is also exerted against the outer surface of spring check valves 206 and 227. These check valves are provided as a delay device for insuring that segments 152 are displaced inwardly to engagerod 12 prior to the introduction of pressurized clamp closing fluid into channels 196 and 220 to displace seals 197 upstream against cylinders 150. In the absence of such a time delay provision, the upstream surfaces of seals 197 might be caused to be deformed into the space between rod 12 and shallow teeth 173 prior to rod engagement which deformation would be undesirable. The time delay provision, however, allows segments 152 to be displaced inwardly, so as to be in engagement with rod 12, prior to the upstream displacement of sealing ring 197 in response to the introduction of clamp closing fluid from annular channels 199 and 222 into annular channels 196 and 220 respectively. In this regard, it was noted above that the downstream displacement of sealing ring 197 is limited so as to provide a high resistance flow path along the tapered surface of sealing ring 197. Such a high resistance flow path allows clamp closing fluid to circulate freely at full pressure against the downstream surface of sealing ring 197 prior to the exertion of full pressure against the tapered surface of sealing ring 197. This disparity in pressure allows the upstream displacement of sealing ring 197 into engagement with the tapered surfaces of annular channels 196 and 220 thereby forcing sealing ring 197 into sealing engagement with both sealing blocks 148 and 208 as well as the outer surface of rod 12. l

The bodies of clamp opening fluid and clamp closing fluid are maintained distinct by the high pressure seal structure provided in seal receiving channels 161. More specifically, and considering only one of the seal structures, when clamping cylinder 150 is in open position, the clamp opening fluid circulates from channel 168 radially outwardly between segments 152 to bear against the tapered surfaces of anti-extrusion strip 164. Strip 164 in turn bears against sealing strip 165 which in turn bears against anti-extrusion strip 163. The tapered surfaces of anti-extrusion strip 163 are thereby forced against the complementarily tapered surfaces of channels 159 and 160 formed in the surface of segments 152 as discussed above. This engagement effects a fluid tight seal which prevents the clamp opening fluid from coming into communication with the clamp closing fluid. When it is desired to close clamping cylinder 150 so as to engage rod 12, the pressure of clamp closing fluid is increased with respect to the pressure of clamp opening fluid, either by increasing the clamp closing fluid pressure or by decreasing the clamp opening fluid pressure, so as to displace segments 152 radially inwardly. In this regard, as clamp closing fluid pressure exceeds clamp opening fluid pressure, anti-extrusion strip 163 is forced out of engagement with the tapered surfaces of seal receiving channel 161 and the tapered surfaces of anti-extrusion strip 164 are causes to engaged the tapered surfaces of seal receiving channel 161. This engagement once again effects a seal which prevents the communication of the clamp closing fluid with the clamp opening fluid. As discussed above with respect to FlGS. 4a and b, the communication of clamp opening and clamp closing fluids around the longitudinal ends of strips 163, 164 and 165, is prevented by provision of suitable seals 180 and 194 in seal 116, and 180 and 217 in seal 130. Thus, it can be seen that rod clamping cylinder 150 is operated between rod engaging and rod releasing positions by controlling the relative pressures of clamp opening and clamp closing fluids which are exerted thereon.

Considering now the provision of opening and closing fluids to the particular clamps, and with respect to stationary rod clamp 116 as shown in FIGS. 2a, 4a and 5a, clamp opening fluid is provided to fluid passages 168 thereof from a source (not shown) through supply line 122 and passage 124 i into annular space 119 whereupon it passes between the surface of rod 12 and second bore 118 to fluid passage 183 and 185 195 in upstream sealing block 146. Clamp closing fluid for stationary rod clamp 116 is provided from inner support fluid chamber 126, through passage 201, channel 199 and passage 204 (FIG. 4a) in downstream sealing block 148 to annular channel 202. Thereafter, clamp closing fluid is circulated to the outer circumferential surface 170 of clamping cylinder 150 through passages 158 (FIG. 5) which are in communication at their upstream ends with annular channel 202.

In addition to acting as clamp closing fluid for stationary rod clamp 116, the support fluid from support fluid chamber 126 also acts as clamp opening fluid for reciprocable rod clamp 130. Specifically, and referring to FIG. 2b, fluid in chamber 126 is in communication with passages 168 in clamp 130 through counterbore 112 and passage 183 in upstream sealing block 146. Clamp closing fluid is provided to clamp 130 from extrusion fluid supply line 37, through passages 101 and 99 into clamp closing fluid chamber 94, and thereafter through an access passage to passages 158 along the outer surface 170 of the clamp.

In the operation of apparatus 10, as is discussed in detail below, fluid pressure is continually maintained in the extrusion fluid which acts as clamp closing fluid for reciprocable rod clamp 130, and upon the clamp opening fluid acting upon stationary rod clamp 116. However, the pressure of the fluid in support fluid chamber 126 is varied cyclically. Thus, because of the constant exertion of clamp opening pressure and the intermittent exertion of clamp closing pressure, stationary rod clamp 116 is a normally open clamp which closes only upon the increase of pressure in the support fluid in chamber 126. Conversely, because of the constant exertion of clamp closing pressure and the intermittent exertion of clamp opening pressure reciprocable rod clamp is a normally closed clamp which opens only upon the increase of pressure in the support fluid in chamber 126.

OPERATION OF THE APPARATUS Broadly stated, the operation of the apparatus of P108. 2a, b and 0 comprises the steps of establishing and maintaining a desired relative velocity of a work-' piece, e.g., rod 12, against a deforming agency comprising a flow of pressurized fluid through fluid control element 136, and continuously deforming the rod against the deforming agency to produce product 14.

The desired relative velocity between the deforming agency and the rod is accomplished by intermittently advancing the rod against the deforming agency, intermittently advancing the deforming agency over the rod, and coordinating the intermittent advance of the rod with the intermittent advance of the deforming agency to maintain a desired relative velocity therebetween so as to maintain a continuous positive fluid flow extrusion of the rod. During extrusion, the relative speed of rod 12 passing through fluid control element 136 is maintained such as to effect and maintain an extrusion equilibrium condition so as to maintain extrusion at a desired product discharge rate.

As noted above, the specific mode of extrusion in operating the apparatus of FIGS. 2a, b and c, is that of positive fluid flow extrusion. This mode of extrusion contemplates establishing a positive flow of pressurized fluid through a fluid control element while concurrently passing material to be deformed through the fluid control element within the flowing fluid. The pressurized flowing fluid exerts pressures on the material passing therewith through the fluid control element, which pressures bear upon the material to accomplish the deformation thereof.

The extrusion equilibrium condition' referred to above, as used in the context of the discussion of the operation of apparatus 10, connotes the situation during extrusion when (a) a constant relative velocity of advance of rod 12 is occurring through fluid control element 136 notwithstanding variations in the mag nitudes of their absolute velocities, (b) stresses generates in rod 12 by the effect of. fluid bearing against the surface thereof in cooperation with the mechanical forces exerted thereon by clamps 116 and 130 are such as to accomplish deformation of the material as desired within fluid control element 136, (c) a controlled flow of fluid is passing through fluid control element 136 so as to exert deformation pressures on the material passing therethrough, and ((1) deformation is occurring with wire 14 being discharged through passage 143 and aperture 50 at a desired rate. During extrusion equilibrium, volumes of product 14 and extrusion fluid are discharged through fluid control element 136 in constant proportion and equal in total volume to the volume of the relative incremental displacement of rod ,12 and its surrounding fluid through fluid control elezone of deformation when the radial stress in the material exceeds the axial stress in the material by an amount at least equal to the yield stress of the material. Control of the rate of decrease of the pressure of fluid flowing through the zone of deformation so as to maintain the stress relationship desired for deformation is accomplished by providing fluid control element 136 with flow control surface 137, which surface is shaped to define a controlled path for regulating fluid flow so as to achieve the desired pressure regulation. The shape of thc flow control surface may be linear or nonlinear, and may be determined empirically as is-disclosed in the above-noted copending application for METHOD OF POSITIVE FLUID FLOW EXTRU- SION.

, through the fluid control element at all times during the be pre-shaped, for example in the manner disclosed Also disclosed in the above-noted copending application is the concept of the positive fluid flow extrusion which is utilized in the present apparatus.

The apparatus of FIGS. 2a, b, and c'accomplishes the above discussed positive fluid flow extrusion with respect to the extrusion of a continuous rod of incycle, including those times when the cycle is shifting from the one phase to the second phase, and thereafter from the second phase back to the one phase. In order to accomplish the foregoing function, various operational movements are required of the apparatus elements, viz. reciprocation of fluid control element 136,

reciprocation of clamp cylinder 23, engagement and disengagement of stationary rod clamp 1 16, and the en-' gagement, disengagement and reciprocation of reciprocable rod clamp 130. In addition to the abovenoted operational movements, the bodies of fluidin-the various fluid systems must be pressurized as required to support the operation of the apparatus.

The operational positions of the various apparatus components during extrusion are set outschematically in FIGS. 6a through h which, when considered in .conjunction with the timing chart of FIG. 7, provides a better understanding of the operation of the apparatus 10. However, considering initially the start-up of extrusion by apparatus 10, all systems of theapparatus are filled with fluid and a rod 12 is positioned within the apparatus by passing the head end thereof through the aperture 15 in base 17 and thereafter advancing the rod axially until it has passed through clamps 116 and and extends within inner extrusion fluid chamber 142.

The apparatus 10 can be started at virtually any point in its cycle. Although a convenient position in the cycle to start the apparatus is shown in FIG. 6a wherein reciprocating the clamp cylinder 23 is in fully retracted position (fully to the right as seen in the figure), stationary clamp 116 is engaging rod 12, reciprocable clamp 130 is not in engagement with rod 12 and fluid control element 136 is in position to advance (move to right within chamber 142) over rod 12.

In order to facilitate start-up, the head of rod 12 can and claimed in copending application for METHOD OF PREFORMING MATERIALS WHICH WORK HARDEN, Ser'. No. 758,732, filed Sept. 10, 1968 and assigned to the same assignee as the present application. However, such preshaping, while advantageous, is

not necessary and .apparatus 10 can be operated whether the head of rod 12 is preshaped or not.

With rod 12 extending into inner extrusion fluid chamber 142, the pressure of the support fluid in I.

after rod 12 is positioned within apparatus since the exertion of such pressure prior to the introduction of pressure to the support fluid system would close rod clamp 130 and preclude initial passage of the rod therethrough.

With pressure in the support fluid, pressure in the extrusion fluid system, stationary rod clamp 116 engaged with rod 12 and reciprocable rod clamp 130 out of engagement with rod 12 and in fully retracted position (FIG. 6a), ram 45 and therewith fluid control element 136 are advanced toward the head end of rod 12. The initial advancement of fluid control element 136 causes a flow of fluid out of inner extrusion fluid chamber 142 and through the fluid control element 136 and passage 143 to be discharged through aperture 50. As the flow control surface 137 of fluid control element 136 approaches the head end of rod 12, the space between the head end of rod 12and the flow control surface 137 decreases in size and progressively restricts the flow of fluid therethrough. The flow restriction, which in effect is a valving action, causes an increase in the pressure of the fluid in the vicinity of the head end of the billet. Continued advancement of fluid control element 136 into chamber 142 continues the build up of pressure therein until extrusion of rod 12 commences in the same manner as is discussed in detail in copending application for METHOD OF POSITIVE FLUID FLOW EXTRUSION supra.

The nature of the deformation occurring to rod 12 to form product 14, described briefly, is caused by disparate radial and axial stress in the rod material as it passes through the zone of deformation defined by the flow control surface 137 of fluid control element 136. Specifically, at every point in the zone of deformation the rod material is subjected to axial and radial stresses, the radial stresses resulting from the radial effect of the pressurized fluid which is flowing through fluid control element 136, and the axial stresses resulting from both the axial effect of the pressurized fluid which is flowing through fluid control element 136 and bearing against the surface of the rod material, and the axial reaction force generated by engaged stationary rod clamp 116. The pressure drop in extrusion fluid flowing through fluid control element 136 in such as to insure that at all points along the zone of deformation, the stresses generated within the material are such as to cause the deformation thereof from the shape of rod 12 to that of product 14, i.e., at all points within the zone of deformation the net radial stress on the material exceeds the net axial stress by an amount equal to at least the yield stress of the material.

Whereas the operation of apparatus 10 is directed ultimately to the deformation of rod 12 to form wire 14, it is desirable that such deformation occur only as desired, i.e., in the zone of deformation of fluid control element 136, and that no deformation occur elsewhere within apparatus 10. Deformation outside the zone of deformation may occur if the net stress at any point in rod 12 outside of the zone of deformation exceeds the yield stress of the material. In this regard, such a net stress can occur if either the radial stress exceeds the axial stress or the axial stress exceeds the radial stress by an amount equal to at least the yield stress of the material.

When radial stress exceeds axial stress by an amount equal to or greater than the yield stress of the material, the rod material is caused to sink, i.e., be displaced longitudinally axially. If, however, the axial stress exceeds the radial stress, the rod material will be displaced radially, i.e., bulge and tend to expand at the point of deformation.

The greatest possible incidence of sinking occurs with respect to the rod material in chamber 142 (FIG. 2c) wherein the fluid surrounding the surface of rod 12 is at a pressure which introduces radial stresses in the billet material which are in excess of the axial stresses experienced in the billet material at this point. In the apparatus 10, deformation within chamber 142 is precluded by dimensioning the diameters of rod 12, third bore 134 and thin cylinder 144 in the downstream portion 28 of clamp cylinder 23 so as to define a narrow annular space of sufficiently small radial dimension to generate a high resistance to any tendency to fluid flow within the annular space. This mode of avoiding sinking is discussed in detail in copending application, METHODS OF POSITIVE FLUID FLOW EXTRU- SION supra.

The greatest incidence of bulging occurs with respect to the rod material upstream of the inner surface 215 of sealing block 208 when stationary clamp 116 is engaged and when the rod is subjected to axial stress along its length from fluid control element 136 to its point of axial support at stationary rod clamp 116. Such bulging is precluded in apparatus 10 by pressurizing the support fluid, which when reciprocable rod clamp is in open position, contacts the surface of rod 12 from the downstream end of stationary clamp 116, through chamber 126 and counterbore 112 and within clamp 130, to a sufficient magnitude to generate radial stresses in the rod material which are of sufficient magnitude to offset the axial stress in the rod material by an amount sufficient to render the net stress less than the yield stress of the material. Thus, it

can be seen that although rod 12 is subjected to relatively high radial and axial stresses during the operation of apparatus 10, provision is made to obviate the possibility of sinking or bulging of the rod material prior to its entrance into the zone of deformation of fluid control element 136.

Returning now to the discussion of FIGS. 6 and 7 and the operation of the apparatus 10, FIG. 6a shows the apparatus configured and operating just after extrusion has commenced, i.e., fluid control element 136 is being advanced by ram 45, clamp 130 is open, clamp 116 is engaged and clamp cylinder 23 is fully retractedand stopped. With the apparatus operating in this manner, it can be seen with reference to FIG. 7, wherein line a" corresponds to the operating situation schematically shown in FIG. 6a, that the fluid in the support fluid system is pressurized and the extrusion fluid is in its pumping phase. The term pumping" phase connotes, for purposes of this disclosure, that outer extrusion fluid chamber 92 is isolated from inner extrusion fluid chamber 142 (i.e., thin cylinder 144 is covering ports 145) and thus, the advance of vfluid control element 136 into inner extrusion fluid chamber 142 causes fluid to be pumped therefrom through fluid control element 136.

As fluid control element 136 nears its fully advanced position, the pressure of the support fluid is reduced, initially by an amount sufficient to allow reciprocable clamp 130 to close and engage rod 12, and thereafter by an amount sufficient to allow the opening of stationary clamp 116. This sequencing is accomplished by the provision of selected fluid pressures in the clamping fluid systems. Specifically, each of the clamps 116 and 130 is operated from engaged to disengaged position by establishing a pressure differential between the pressures of the clamp opening and clamp closing fluids. Thus, such a pressure differential can occur at a relatively high pressure as well as a relatively low pressure level. Relating this to the sequencing operation of the clamps noted above, the support fluid in channel 168 (FIG. 4b) of clamp 130 acts as clamp opening fluid against the effect of extrusion fluid as clamp closing fluid. With respect to clamp 116, however, the support fluid acts as clamp closing fluid operating against the effect of the stationary clamp opening fluid supplied through line 122. Selectively, the clamp opening fluid for clamp 116 is maintained at a pressure which is less in magnitude than the pressure of the extrusion fluid provided through line 37. Thus, it can be seen that the support fluid will overcome the relatively low pressure stationary clamp opening fluid pressure so as to close clamp 116 at a much lower pressure level than it can overcome the relatively high pressure extrusion fluid pressure so as to open clamp 130.

FIG. 6b represents the point in the extrusion cycle where support fluid pressure has dropped sufficiently to allow reciprocable rod clamp 130 to engage rod 12, fluid control element is advancing at an absolute velocity which is equal to the desired relative velocity for maintaining extrusion equilibrium, clamp l 16 is still engaged and reciprocable clamp cylinder 23 is still in a stopped condition. This situation is. shown in FIG. 7 as lineb.

With the continued advance of ram 45 and fluid control element 136, the pressure of the support fluid in chamber 126 (FIG. 2b) is continually reduced until it is insufficient to maintain clamp 116 engaged with rod 12 and the clamp is opened to a disengaged position by the pressure of stationary clamp opening fluid in the channels 1680f clamp 116. Concurrently with the opening of clamp 116, advance of fluid control element 136 is slowed and fluid motors 29, 21, 42 and 43 are operated to cause advancement (from right to left as shown in FIG. 6) of clamp cylinder 23 and therewith clamp 130 and rod 12. The velocity of fluid control element 136 is decreased and'the velocity of cylinder 23 and therefore rod 12 is increased until fluid control element 136 is stopped and the rod 12 is being advanced at an absolute velocity equal to the desired relative velocity for maintaining an extrusion equilibrium. This operating situation is shown in FIG. 6c as well as at line in FIG.

With regard to the variation of the absolute velocities of fluid control element 136 and rod 12, it was noted above that establishing and maintaining an extrusion equilibrium condition involves maintaining a constant relative velocity between the fluid control element and the rod being advanced thereinto. Thus, in the progress of the operation from FIG. 6b to FIG. 6c, the decrease in velocity of fluid control element 136 and ram 45 is coordinated with the increase in velocity of cylinder 23 and rod 12 so that at all times'the desired relative velocity is maintained.

This coordination between the velocities of the rod and fluid control element is maintained at all times during extrusion by apparatus 10 and is accomplished by.

coordinating the motive fluid provided to fluid motors 20, 21, 42 and 43 with the motive fluid provided to the fluid motor (not shown) which operates ram 45 through piston rod 47 (FIG. 1 Such coordination may be accomplished by any of a plurality of known methods in the hydraulics art. For example, one of fluid motors 42 or 43 may have a servo valve connected thereto for reciprocation with the ram or piston of the fluid motor. The servo valve may be driven in response to the movement of a cam mounted on a common rotating cam shaft, which cam may be shaped to I establish movement of the reciprocating clamp in accordance with the value of reciprocating clamp velocity as shown in the timing chart of FIG. 7. Operation of the servo valve on fluid motor 42 in response to the positioning of the cam will control the flow of fluid into or out of both fluid motors 42 and 43.

Similarly, the fluid motor (not shown) which operates ram 45 through piston 47 may also be provided with a servo valve which is actuated in response to the positioning of a cam mounted on the abovenoted common cam shaft. Operation of such a servo valve will control the flow of fluid into and out of the fluid motor and thus control the speed of advance and retraction of ram 45 and piston 47. The cam for this fluid motor would be shaped in accordance with the curve of fluid control element velocity as shown in FIG. 7. Further, since both of the cams for operating the fluid motors are mounted on a common rotating cam shaft, the velocities and positions of the reciprocating clamp and fluid control element are positively controlled at all times during operation of the apparatus.

With respect to the fluid motors 20 and 21, these mo- I tors are provided for the purpose of maintaining reciprocating clamp cylinder 22 in a state of compression at all times during the operation of the apparatus. To this end, each of fluid motors 20 and 21 can be provided with a pressure regulating valve and suitable source of messurized fluid for maintaining a compressive force against reciprocating clamp cylinder 22 notwithstanding whether it is advancing or retracting.

Further, it is considered to be clear that the other fluid systems utilized in operating the apparatus of the invention may be controlled in any of the many manners known to those skilled in the art. The manner of coordinating the fluid motor hydraulic systems is within the capability of those skilled in the hydraulically operated machinery art and as such a detailed description of such a hydraulic system is not deemed necessary.

With the responsibility for maintaining the desired relative velocity between rod 12 and fluid control element 136 now shifted to cylinder 23 and clamp 130, the retract on of ram 45 and fluid control element 136 commences, FIG. 6d, so as to position fluid control element 136 for its next advancement stroke. This positioning, since the extrusion operation is continuous, necessitates that advancement of rod 12 by clamp and cylinder 23 is maintained at an absolute velocity 

1. Apparatus for clamping a workpiece, which apparatus is operable between a workpiece engaging position and a workpiece disengaging position, said apparatus comprising: a. a clamping cylinder including a plurality of longitudinally extending cylinder segments adapted to surround a workpiece, said cylinder segments being displaceable radially inwardly to engage said workpiece and radially outwardly to disengage said workpiece; b. each cylinder segment including an inner surface adapted to engage said workpiece, an outer surface and a pair of radially extending surfaces between said inner surface and said outer surface; c. first channel means formed in a radially extending surface of each of said cylinder segments, each of said first channel means cooperating with the radially extending surface of each next adjacent cylinder segment to define a passage for introducing a first pressurized fluid to displace said cylinder segments radially outwardly into workpiece disengaging position; d. fluid pressure means operable against the outer surfaces of said cylinder segments for displacing said cylinder segments radially inwardly to workpiece engaging position.
 2. Apparatus as in claim 1, said apparatus comprising: e. second channel means formed in each radially extending surface of each of said cylinder segments, the second channel means of adjacent radially extending surfaces cooperating to define a seal receiving channel between adjacent cylinder segments; f. seal means mounted in each seal receiving channel to separate said first pressurized fluid from said fluid pressure means.
 3. Apparatus as in claim 1 wherein the inner surface of each cylinder segment is provided with a plurality of teeth.
 4. Apparatus as in claim 1 wherein the outer surface of said cylinder segments are bevelled to define fluid circulating passages. 